Human Subraces

In the playtest package humans are the only race without a "subrace" despite being the most diverse and adaptive race. And, because they're less of a "hook" for the race and racial powers humans get very blank bonuses.

What about changing that? Say, taking a page from Dragonlance and having "civilized" or "barbarian" humans. Give one a bonus to mental skills and the other a bonus to physical skills. Add new powers accordingly, such as hardiness or wilderness survival powers for one and others suggesting intelligence and decadence.

The names are flexible. "Urban" and "nomadic" would work. As would "urbane / erudite" and "wild / rural".

It instantly adds some distinction to humans. The suggestion of story and world building. Humans aren't all identical
There are the savage Cimmeria and the softer south folk. There are the Northfolk and the southern people beyond the wall. The hardy barbarian tribes of the traders from Ten-Towns. There are the rough Germanic folk or the culture Romans.

Different human cultures should definitely be in the game, but they don't need to be mechanically distinguished. If the human race options are done consistent with prior approaches to make humans the "versatile" race, you should have choices sufficient to adjust to what you want, without having that choice baked in. Let something in the game be non-mechanical, please.

Humans shouldn't simultaneously be the "versatile" race and at the same time an "optimized" race based on a bunch of subraces.

And in case you ask, I'd be fine without non-human subraces, too. Mountain dwarves and wood elves can be culturally but not mechanically distinct from hill dwarves and high elves as far as I'm concerned.

"The Soul of D&D?It's rolling a natural 20 when you're down to 3 hit points and the cleric's on the floor and you're staring that sunnavabitch bugbear right in his bloodshot eye and holding the line just long enough to let the wizard unleash a fireball at the guards who are on their way, because they're all that stands between you, the Foozle and Glory." - WizarDru

Pathfinder's tried to do this, and they gave it a good go, but ever time I look at their take on the subject I find myself coming back to the bonus feat/skill. One of 3e's little bits of genius was humans; a bonus feat and skill points gives you all you'll ever need out of a race (whereas 2e humans were often a mechanically suboptimal choice). There's no need to mess with this. Stick with what works.

I don't get 5e's superman "everything you can do I can do better" take on humans: +1 to all stats, and +2 to one of your choice. However, I don't think sub-races is a wise move. Instead, if I was going for humans as the most adaptable race I might do something like:

+1 to a stat of your choice
A bonus background of your choice
A bonus feat from a specialty or talent from a class

In the playtest package humans are the only race without a "subrace" despite being the most diverse and adaptive race. And, because they're less of a "hook" for the race and racial powers humans get very blank bonuses.

What about changing that? Thoughts?

While I like the idea from a strictly game-design perspective, it could be tricky to sell in a corporate environment. Fantastic species are one thing, statting out groupings of humans differently by (sub)race is another can of worms entirely. You might get away with it if you stick to cultural differences in made-up fantasy-setting cultures - that bear /no/ slightest similarity to any RL culture...

It would make sense to do it the way you outlined it. Basing it around lifestyle (urban/woods/sea/whatever) as Greg K described rather than appearance is logical and should be inoffensive. It would probably even add some cool options.

Unfortunately it wouldn't be worth the hassle it would cause. After seeing all the outrage over proposals for implementing even the most simple and obvious variation among humans mechanically (average male strength is higher than average female strength), I think WOTC would be crazy to put this in their books. They'd end up spending more time and resources trying to put out the firestorm than they would developing the game.